Mullus barbatus L. and Mullus surmuletus L. from western Mediterranean waters (SE Spain) are infected by Hysterothylacium fabri, but not by zoonotic nematodes. Possible impact on fish hosts

Abstract

In order to know the risk of anisakiasis (or anisakidosis) by consumption of fish of the genus Mullus from the western Mediterranean Sea in our geographical area, where they are appreciated for their quality, an epidemiological survey was carried out to detect zoonotic or potentially zoonotic nematodes in M. barbatus and M. surmuletus. Although the presence of third larval stage (L3) of anisakids (Anisakis and Contracaecum) has been previously described in these fish, the results showed absence of anisakids and presence of L3 and L4 of raphidascaridids of the genus Hysterothylacium which were molecularly identified as H. fabri. Phylogenetic analysis group them into the Mediterraean Sea clade and far from individuals isolated in the Pacific Ocean. Prevalence was somewhat higher, but not significant, in M. barbatus vs M. surmuletus (72.3 vs 60.0 %), but mean intensity (MI) and mean abundance (MA) parameters were approximately twice as high in M. barbatus as in M. surmuletus (MI 5.8 vs 2.8, p=0.001; MA 4.2 vs 1.7, p<0.001). The presence of the parasite seems to affect these two sympatric species differently. In M. barbatus it seems to affect their growth, as it appreciably reduces the value of allometry coefficient in infected fish (2.78 vs 2.18). On the other hand, in M. surmuletus the infection significantly (p<0.04) affects the Fulton's condition factor, an indicator of the health status of the fish. It can be concluded, that the ingestion of these fish by the population poses no risk of anisakiasis, but the consumer should continue to be urged to follow the rules of prevention against this illness. #Note that throughout the manuscript the authors use the term ‘red mullets’ in the plural to refer collectively to the two species of the genus Mullus surveyed. When used in the singular, they refer only to Mullus barbatus (red mullet). Not to be confused with mullets, family Mugilidae.